The use of power operated rotary chucks in machining operations is well known in the art. When the chuck is operating at high speed, there is a tendency for the jaws to loosen their grip upon the workpiece due to the centrifugal force acting upon the jaws. The loosening tendency would be most apt to happen when light gripping pressures are used on parts which might be distorted by increased pressure. One such workpiece which is subject to damage from excessive gripping pressure is thin wall tubing. The need for a device to overcome the problems associated with centrifugal unloading, has lead to the development of various counterweighting mechanisms. These mechanisms are associated with jaw activating devices wherein centrifugal forces acting to disengage the jaw gripping members are counterbalanced by various weighting devices.